netdev - Re: [PATCH net] be2net: call napi_disable() for all event queues

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Date:	Wed, 27 Nov 2013 09:00:00 +0100
From:	Ivan Vecera <ivecera@...hat.com>
To:	Sathya Perla <Sathya.Perla@...lex.Com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Subramanian Seetharaman <subbu.seetharaman@...lex.Com>,
	Ajit Khaparde <Ajit.Khaparde@...lex.Com>
Subject: Re: [PATCH net] be2net: call napi_disable() for all event queues

On 11/27/2013 06:28 AM, Sathya Perla wrote:
>> -----Original Message-----
>> From: Ivan Vecera [mailto:ivecera@...hat.com]
>>
>> The recent be2net commit 6384a4d (adds a support for busy polling)
>> introduces a regression that results in kernel crash. It incorrectly
>> modified be_close() so napi_disable() is called only for the first queue.
>> This breaks a correct pairing of napi_enable/_disable for the rest
>> of event queues and causes a crash in subsequent be_open() call.
>>
>> Cc: Sathya Perla <sathya.perla@...lex.com>
>> Cc: Subbu Seetharaman <subbu.seetharaman@...lex.com>
>> Cc: Ajit Khaparde <ajit.khaparde@...lex.com>
>> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
>> ---
>>   drivers/net/ethernet/emulex/benet/be_main.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/emulex/benet/be_main.c
>> b/drivers/net/ethernet/emulex/benet/be_main.c
>> index 78a0e85..0aec4d2 100644
>> --- a/drivers/net/ethernet/emulex/benet/be_main.c
>> +++ b/drivers/net/ethernet/emulex/benet/be_main.c
>> @@ -2663,8 +2663,8 @@ static int be_close(struct net_device *netdev)
>>   			napi_disable(&eqo->napi);
>>   			be_disable_busy_poll(eqo);
>>   		}
>> -		adapter->flags &= ~BE_FLAGS_NAPI_ENABLED;
>>   	}
>> +	adapter->flags &= ~BE_FLAGS_NAPI_ENABLED;
>>
>
> Ivan, Thanks for spotting this.
> Your fix is correct but it'll be nice if the for-loop for napi_disable
> is not even entered when FLAGS_NAPI_ENABLED is not set, as in:
>
> diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
> index 603b662..40d2adb 100644
> --- a/drivers/net/ethernet/emulex/benet/be_main.c
> +++ b/drivers/net/ethernet/emulex/benet/be_main.c
> @@ -2658,8 +2658,8 @@ static int be_close(struct net_device *netdev)
>
>   	be_roce_dev_close(adapter);
>
> -	for_all_evt_queues(adapter, eqo, i) {
> -		if (adapter->flags & BE_FLAGS_NAPI_ENABLED) {
> +	if (adapter->flags & BE_FLAGS_NAPI_ENABLED) {
> +		for_all_evt_queues(adapter, eqo, i) {
>   			napi_disable(&eqo->napi);
>   			be_disable_busy_poll(eqo);
>   		}
>
> Could you also add the following line to your patch as it fixes a
> regression caused by an older be2net commit:
> Fixes: 6384a4d0dcf9 ("be2net: add support for ndo_busy_poll")
>
Sure, I'm sending v2.

Ivan

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